Q: We tried to measure speed losses and minor stops electronically, yet although tons of data where gathered, it was difficult to see what we needed to do. How can I visualize all speed losses, including minor stops, in a way that we can reduce them?
Arno Koch • Electronic data acquisition to detect minor stops and other speed losses, usually consumes quite some effort. And indeed, enormous amounts of data are being gathered. The typical assumption in such an IT approach is that when there is data, this will lead to information, in this case: information what to do. This is at least doubtful, as you discovered. Such systems more often lead to focus on the data, and not at the information that should lead to the needed improvement…
The question I will try to answer here is:
How to proceed with OEE to reduce speed losses?
1. First find the reduced speed losses:
1.1 Define the theoretical maximum speed of the equipment
1.2 Allow the operator to register the ‘Set Speed’; this is the speed he sets the machine to work at
1.3 The difference between the theoretical maximum speed and the set speed will result in ‘reduced speed loss’
Example:
The machine has a theoretical maximum of 100 units/min
The operator sets the machine on a set-speed of 80 units/min
Now 20 units will not be produced due to the deliberately reduced speed of the equipment.
2. Discover the causes of “Reduced Speed Losses”
The operator will reduce the speed of his equipment when he experiences
- Quality problems
- Process disturbances
- Technical failures
- Timing problems
An experienced operator might typically tell you: “If I set the equipment to run at 80 units/min, I will have the highest output and few problems”
3. Find ‘visible minor stops’
By definition, many OEE registrations have a threshold somewhere between 1 and 10 minutes, to detect a machine stop. If the machine stops longer than the threshold value (usually 5 minutes) the stop is considered to be an availability loss and needs to be identified with i.e. a failure- or an idling- code. If the stop is shorter than the threshold, it is considered to be a minor stop and will not be identified with a stop-code. This makes sense, because if we ask the operator to tell us the reason for each machine stop, even the very small ones, the registration-stress will become unbearable.
4. Find the ‘Invisible Minor Stops’
In the next topic, I describe a method to approach Minor stops in ore detail, assuming you have good OEE Software
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